Surgical scalpels typically include a replaceable, surgical steel scalpel blade that is secured, either permanently or removably, at one end of a metal handle. While these prior-art scalpels work well to perform various surgical procedures, users of such scalpels often sustain accidental injuries which is obviously highly undesirable. For example, scrub nurses may be injured when loading and unloading replaceable scalpel blades. Similarly, surgeons and surgical assistants may be injured as the scalpel is transferred back and forth among the members of a surgical team or during surgical dissection when the blunt end of the surgical instrument (opposite the blade) is used as a special-purpose instrument, such as for defining surgical planes, which is a common practice among surgeons.
To alleviate the problem of injuries caused by conventional, prior-art scalpels, several attempts have been made to develop a scalpel in which the blade of the scalpel can be retracted into the handle of the scalpel. Examples of these attempts are disclosed in Haining U.S. Pat. No. 5,330,493, issued Jul. 19, 1994 ("the '493 Patent"), Roberts, et al. U.S. Pat. No. 5,344,424, issued Sep. 6, 1994 ("the '424 Patent"), Cote, et al. U.S. Pat. No. 5,431,672, issued Jul. 11, 1995 ("the '672 Patent"), and DeCampli U.S. Pat. No. 5,571,127, issued Nov. 5, 1996 ("the '127 Patent"). Each of these patents discloses a scalpel having a blade which may be retracted or extended by the actuation of a single pushbutton followed by a manual sliding of that pushbutton to effect either retraction of the blade of the scalpel into the handle of the scalpel or extension of the blade from the handle.
Although these scalpels may reduce, to a limited extent, the injuries described above, they also have a number of drawbacks of their own. It is important in the performance of surgical procedures that the blade of a scalpel be fixed relative to the handle, because any movement of the blade relative to the handle that is not intended or expected by a surgeon can result in serious injury to a patient in surgery. Some patient injuries also can occur because, in the case of some prior-art scalpels, the blade does not extend far enough out of the handle to enable a surgeon to effectively use the entire cutting edge of the blade for cutting rather than merely the point. The use of the point of a scalpel blade for cutting increases the risk of a surgeon "sticking" the patient with the scalpel blade, which also is highly undesirable.
Moreover, the scalpels disclosed in the foregoing patents suffer from the additional drawback that the blade of each of those scalpels can make slight lateral movements relative to handle (i.e., transverse to a longitudinal axis of the handle), even when the blade is locked in an exposed position. Further, because of the single-action (i.e., one-button) structure used for extension and retraction of the blade of the each of those scalpels, it is common for a surgeon to actuate the button inadvertently while maneuvering the scalpel and thereby unintentionally cause the scalpel blade to retract partially or fully into the handle of the scalpel, which is highly undesirable, especially during emergency surgical procedures and the like.